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View Full Version : Throwing aluminum cans into the sea?



BrianW
05-26-2006, 05:16 PM
I was wondering how long an aluminum can last when thrown into saltwater. Did a Google search, but didn't come up with anything.

I realize there's rules and even have the proper garbage placard on my boat. But, I did read were a aluminum can may last 500 years if thrown away. The article didn't specify where, but I assume they are talking about a landfill. If a can thrown in the ocean only last half that, wouldn't it be better?

Of course the best thing is to recycle, but that's different topic.

PeterSibley
05-26-2006, 05:26 PM
Recycle it Brian, aluminium is just perfect for recycling.

As for how long it would last ,it would depend largely on the chemical reaction...and that would depend on water temperature.It wouldn't last long in the Gulf of Mexico...longer off Maine.

ljb5
05-26-2006, 05:32 PM
It kinda depends on what you mean by "last."

It'll probably sit there as a recognizable can for a few hundred years....

Eventually, it'll corrode to the point that it falls apart (depending on the chemical reactions)....

You wouldn't see it anymore...but that doesn't mean it's gone.

In terms of environmental impact, it would be much more benign before it disintegrates than after.

BrianW
05-26-2006, 05:39 PM
Thanks Peter, your on to something there with the different water temperatures.

And yes, of course recycling is the only way to go.

But... let's say your cruising in an area that doesn't recycle aluminum cans, but rather throws them in the land fill. You can take your cans ashore for disposal in the landfill, or wait till your way out to sea and toss them overboard.

What then?

But actually, I was more interested in some simple data on aluminum can life in the ocean. :)

brad9798
05-26-2006, 05:54 PM
How 'bout all the cigaretter butts I tend to see in the water ... that bugs the **** out of me. Even moreso than cans ... I can easily net a can and recycle it ...

huisjen
05-26-2006, 06:59 PM
Water depth and oxygen content will play a role too. And salinity. Throwing it into an estuary will have much quicker results than throwing it into a deep ocean environment. In the area off Oregon, it would get burried in the subduction zone by Columbia River silt before it disintegrated, I'd guess.

Dan

Bob Cleek
05-26-2006, 07:46 PM
Actually, I recall being told by somebody, as they tossed an aluminum can overboard, that the thin gauge Coke and beer cans really don't last long at all. They just corrode to powder in no time, although the tops last a bit longer. He used to tear them in half before tossing them so they'd sink fast. Not that you'd want to do it in a pristine resevoir, but in the middle of the Pacific, what the heck?

I once left the boat in a rush and left some knives and forks sitting in soapy water in a cheapo aluminum percolator coffee pot in the galley sink. When I came back the next weekend, the utensils had eaten pinholes through the aluminum where they touched the bottom of the pot! Strange stuff that electrolysis and aluminum! Goes real fast.

ljb5
05-26-2006, 08:09 PM
Come to think of it, aluminum oxide is about the second most abundant material in the Earth's crust -- especially when considering all the various ways it can combine with silica or other elements...

...so after it corrodes, it would have about the same impact as pouring sand on the beach.

Aluminum is situated quite low on the Ellingham diagram:

http://www.corrosion-doctors.org/HotCorrosion/images/Ellingham.gif

...meaning it oxidizes readily and was one of the last metals to become technologically feasible....

In common applications, aluminum doesn't rust. Like all metals (except gold) it yearns to react with oxygen (all the more for it's position in Ellingham's diagram), but unlike iron oxide which crumbles, aluminum oxide forms a durable, impenetrable 'skin' which inhibits further corrosion....

...But that's only in air. In the presence of other elements, aluminum corrodes readily. I'm not sure exactly how it would behave in salt water, but I have an ice cream scoop that testifies to the rapid corrosive power of some element found in dish detergent.

Therefore, I'd conclude a discarded aluminum can will decompose relatively quickly and have no discernable effect on this giant hunk of aluminosilicate on which we tread.

Unless it's an eyesore, or likely to clog some machine, go ahead and throw it overboard --- just don't tell anyone I told you to. :)

ishmael
05-26-2006, 08:15 PM
Of the trash humans throw on the waters, plastics are by far the worst offense. An empty can just sinks, a six pack riing floats, and get's hooked up with sea turtles, etc.

PatCox
05-26-2006, 08:27 PM
I have picked up aluminum cans while scuba diving that have been in the water for a time, and they seem to decompose rapidly. They don't seem old, the ones I have found, yet they are often just a flimsy skin of oxidized aluminum that crumbles when you touch it. Considering aluminum cans have only been common for 40 years or so, the idea that they last hundreds of years doesn't jibe with what I have seen.

Peter Malcolm Jardine
05-26-2006, 08:31 PM
The largest component of solid waste landfills is paper.

Fitz
05-26-2006, 08:49 PM
Well, if everyone recycled the can, maybe we wouldn't need more bauxite mines - often surface excavations in sensitive areas.

http://www.world-aluminium.org/production/mining/methods.html

BrianW
05-26-2006, 10:49 PM
Your guys opinions reflect mine, and Pats hands on experience just about wraps it up. Aluminum cans don't last for years in saltwater.

Not suggesting it's the right thing to do, but in some cases it's not all that bad.

Tearing them in half does make'em sink faster, or so I've been told.

landlocked sailor
05-26-2006, 11:12 PM
We were anchored off Annapolis a couple of weeks ago. The guy in the next boat was tying up his dinghy and tossed about six empty cans in the water. Crowded harbor too: it was the weekend the Volvo 70s were there. Jeez what a jerk! Rick

PeterSibley
05-27-2006, 03:04 AM
Actually, I recall being told by somebody, as they tossed an aluminum can overboard, that the thin gauge Coke and beer cans really don't last long at all. They just corrode to powder in no time, although the tops last a bit longer. He used to tear them in half before tossing them so they'd sink fast. Not that you'd want to do it in a pristine resevoir, but in the middle of the Pacific, what the heck?

I once left the boat in a rush and left some knives and forks sitting in soapy water in a cheapo aluminum percolator coffee pot in the galley sink. When I came back the next weekend, the utensils had eaten pinholes through the aluminum where they touched the bottom of the pot! Strange stuff that electrolysis and aluminum! Goes real fast.

I had a look in the bilge of a one year old aluminium super launch,2 or 3 million worth here .An electrician had left copper wire scraps in the bilge water:rolleyes:...not a pretty sight, a strange ,sliding green goop ,like something out of Ghostbusters.And a VERY shiny aluminium bilge.